Recently, vehicle keyless systems have been widely used. For example, Japanese Patent Laid-open No. 2009-127244 proposes improvement to the convenience of such systems.
Conventionally, communication between a portable device and an on-vehicle device in such a vehicle keyless system has redundancy for improving communication accuracy by including a plurality of unit command signals intermittently transmitted at a predetermined time interval in a command signal transmitted from the portable device.
The on-vehicle device includes a reception unit, a target actuator of the command, and a CPU or the like as a control unit configured to control these components.
When having acquired any one of unit command signals received by the reception unit, the control unit of the on-vehicle device can execute a command by performing code analysis on the signal. To achieve accuracy improvement, however, the control unit preferably acquires all transmitted unit command signals.
To achieve this, in the on-vehicle device, the reception unit sequentially and temporarily stores each received unit command signal in a predetermined memory and transmits an interrupt signal to the control unit, and then the control unit acquires the unit command signal from the memory through acquisition communication in a constant time.